1. Field of the Invention
The present invention relates to a mobile radio communication system and, in particular, to a hand-off method in a digital personal communication service (PCS) system adopting a code division multiple access (CDMA) system.
2. Description of the Related Art
Referring to FIG. 1, a conventional hard hand-off method in a digital PCS system according to the prior art is shown. In this conventional digital PCS system, interprocess communication (IPC) is unavailable since, as illustrated in FIG. 1, there are no link paths formed between the plurality of gateway communication interconnection networks (GCINs) comprising the system. As a result, a hand-off procedure between the GCINs or between local communication interconnection networks (LCINs) is achieved by using a hard hand-off path (denoted as P1) between mobile switching centers (MSCs), with the hard hand-off path being interlocked with the MSC. A hand-off algorithm for providing such a hard hand-off path, however, results in a high probability of call disconnection, since it must perform many processing steps. Specifically, the probability that the call will be disconnected during the hand-off process (for call interruptions over 100 msec) is approximately 50%, which is relatively high.
One of the main causes for this disconnection problem is because the hard hand-off between the MSCs adopts a break-and-make method hand-off method. The break-and-make hand-off method involves temporarily disconnecting the call during processing for over 100 msec, during which time the MSC searches for a Base Transceiver System (BTS) having a stronger RSSI (received signal strength indication) signal of a mobile station at a new cell boundary. Consequently, the conventional hard hand-off method results in a high probability of call disconnection.